Monopropellant rocket engines, commonly referred to as thrusters, generate thrust by using a catalyst to energetically instigate the reaction of a propellant into hot gases. The most commonly used monopropellant, hydrazine (N2H4), is toxic and must be handled in closed containers. To overcome these problems, low-toxicity propellants have been developed as alternatives to hydrazine. These low-toxicity propellants are commonly referred to as ‘green’ propellants. One of the most popular green propellants is hydrogen peroxide (H2O2), which decomposes exothermically in the presence of a suitable catalyst, generating water vapour and oxygen.
In general, it is desirable to use higher concentrations of hydrogen peroxide in monopropellant thrusters, as higher concentrations result in higher temperatures during decomposition. The hot gases are expelled through a nozzle to produce thrust in a specific direction, with higher gas temperatures resulting in more thrust being generated. Conventional hydrogen peroxide monopropellant thrusters utilise a silver catalyst to decompose the hydrogen peroxide. However, silver-based catalysts rapidly deteriorate at high temperatures, making the conventional catalysts unsuitable for prolonged use at high concentrations of H2O2 (>80%). There is therefore a need for a more robust hydrogen peroxide catalyst.
The invention is made in this context.